CVE-2017-9726 in Ghostscript GhostXPS
Summary
by MITRE
The Ins_MDRP function in base/ttinterp.c in Artifex Ghostscript GhostXPS 9.22 allows remote attackers to cause a denial of service (heap-based buffer over-read and application crash) or possibly have unspecified other impact via a crafted document.
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Analysis
by VulDB Data Team • 12/14/2022
The vulnerability identified as CVE-2017-9726 resides within the Ins_MDRP function located in the base/ttinterp.c file of Artifex Ghostscript GhostXPS version 9.22. This flaw represents a heap-based buffer over-read condition that can be exploited by remote attackers through the manipulation of crafted documents. The vulnerability specifically affects the interpretation of TrueType font instructions within the Ghostscript rendering engine, which is commonly used for processing XPS (XML Paper Specification) documents and other print-related formats. The issue stems from inadequate bounds checking during the processing of font data, particularly when handling certain font instruction sequences that trigger the Ins_MDRP function. This function is responsible for interpreting and executing specific TrueType font instructions, and the lack of proper input validation allows attackers to craft malicious documents that cause the application to read beyond allocated memory boundaries.
The technical impact of this vulnerability manifests through a heap-based buffer over-read condition that can result in application crashes and denial of service scenarios. When a malicious document is processed, the Ins_MDRP function attempts to read data from memory locations that extend beyond the allocated buffer space, potentially causing the application to access invalid memory addresses. This behavior can lead to unpredictable application behavior including segmentation faults, memory corruption, and complete application termination. The vulnerability's potential for unspecified other impacts suggests that in certain circumstances, attackers might be able to leverage this condition to execute arbitrary code or gain additional privileges within the affected system. The heap-based nature of the overflow indicates that the memory corruption occurs within the heap memory management area, which can be particularly challenging to exploit reliably but still presents significant security risks. The vulnerability aligns with CWE-125, which describes out-of-bounds read conditions, and may also relate to CWE-787, representing out-of-bounds write conditions that can occur in similar contexts.
The operational impact of CVE-2017-9726 extends beyond simple denial of service scenarios, as it can affect any system running Ghostscript GhostXPS 9.22 that processes untrusted documents. This vulnerability is particularly concerning for environments where users might encounter malicious documents through email attachments, web downloads, or shared network resources. The remote exploitability means that attackers can potentially trigger the vulnerability without requiring local access to the target system, making it a significant risk for web applications and services that process document uploads. Organizations using Ghostscript for document rendering, printing services, or content management systems are particularly vulnerable, as these applications often process documents from untrusted sources. The vulnerability can be exploited across various platforms where Ghostscript is deployed, including Windows, Linux, and Unix-based systems, making it a widespread concern for enterprise environments. From an ATT&CK framework perspective, this vulnerability maps to the T1059.007 technique for command and scripting interpreter, as the exploitation can lead to arbitrary code execution, and potentially to T1566 for initial access through malicious documents.
Mitigation strategies for CVE-2017-9726 should prioritize immediate patching of affected systems, as the vulnerability affects a core component of Ghostscript's document processing capabilities. Organizations should upgrade to Ghostscript version 9.23 or later, which includes fixes for this and related buffer over-read conditions. In environments where immediate patching is not feasible, administrators should implement document filtering and validation mechanisms to prevent processing of suspicious or untrusted documents. Network-level controls such as content filtering appliances and email security solutions should be configured to scan and block potentially malicious documents before they reach end-user systems. Additionally, system hardening measures including heap protection mechanisms, address space layout randomization, and stack canaries can provide additional defense-in-depth layers against exploitation attempts. Regular security assessments and vulnerability scanning should be conducted to identify other potentially affected components within the document processing pipeline. The vulnerability highlights the importance of maintaining current software versions and implementing robust input validation practices throughout the software development lifecycle, particularly in security-critical components that handle external data processing.